1. Field of the Invention
This invention relates generally to the electrode field, and more specifically to new and useful methods for forming an electrode device with reduced impedance. Such electrode are useful when fabricated into neural electrode assemblies for electrically stimulating body tissue or for recording physiological conditions of the body tissue.
2. Description of Related Art
Ideally, conductive electrodes, such as electrodes for sensing and/or stimulation in neural probes, or other neural interface devices, have minimal impedance magnitude and impedance variance (e.g., for an electrode at different times). High impedance generally corresponds with several disadvantages. Sensing and recording electrodes with high impedance typically experience high thermal noise. Stimulation electrodes with high impedance require larger amounts of power during stimulation. Furthermore, a large amount of variance in impedance typically results in poor reliability and predictability during both sensing and stimulation modes of operation.
Increasing the geometric surface area or “footprint” of an electrode is one technique to reduce impedance magnitude and variance, but that approach reduces the electrode's spatial resolution. Increasing the electrochemical surface area of an electrode is another technique for reducing impedance magnitude and variance, but at significant cost and resources. Current methods, such as electrodeposition or electroplating, for increasing a neural electrode's electrochemical surface area are often performed post-process on individual devices after microfabrication and, therefore, are relatively expensive. Electrodeposition can also be performed in batch processes, but this usually has issues with uniformity and repeatability. Also, reliability issues, such as changes in the charge carrying capacity over time or delamination between the modified electrode material and the underlying substrate, can be a concern.
Thus, there is a need in the electrode field to create a new and useful method for reducing the impedance of a neural electrode device. The present invention provides such new and useful methods for manufacturing electrode device, particularly those that are adapted for use in neural interface applications.